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Glossary

| A - C | D - E | F - H | I - O | P - Q | R - S | T - Z|

Family Mold
A multiple cavity mold which produces non-identical parts simultaneously.

Feed Section
The section of the screw just under and slightly forward of the feed hopper.

Fill Pattern
The contour the melt takes sequentially as it fills the cavity. The mold should fill with a straight flow front with no changes in direction throughout filling. Mold-filling analysis software can be used to predict these filling patterns.

Fill Pressure
The pressure required to fill the cavity.

Filler
A relatively inert substance added to a plastic compound to reduce its cost and/or to improve physical properties, particularly hardness, stiffness and impact strength.

Filler
Fillers are generally inert materials characterized by a low aspect ratio (4D). They are commonly used as extenders; fillers do in fact improve certain material properties such as wear, resistance, electrical properties, modulus values, HDT and others.

Film
Films are distinguished from sheets in the plastics industry only according to their thickness. In general, films have thicknesses no greater than .030".

Finish
The surface texture of a finished article.

Fisheyes
Describes a very small void which has not blended completely with the surrounding material. Usually caused by a minute quantity of silicone, oil or other surface contaminate on the surface of the substrate.

Flame Resistance
Deprecated term: not recommended, owing to risk of misunderstanding.

Flame Retardant
Having the ability to resist combustion (A flame retardant plastic is considered to be one that will not continue to burn or glow after the source of ignition has been removed.) Retardant, or retarder: a substance used in small proportion to reduce the reaction rate of a chemical system. Flame retardant: a substance added, or treatment applied, to a material in order to suppress, significantly reduce or delay the propagation of flame. Flame retardants may be added to plastics materials (external flame retardants) or incorporated as chemical groups in the base polymer during the polymerization process (internal flame retardants). Flame retardance is the property of a material, either inherent or by virtue of a substance added or a treatment applied, to suppress significantly, reduce or delay the propagation of flame. Flame retarded: treated with a flame retardant. fire retardant: a substance added, or treatment applied, to a material in order to suppress, significantly reduce or delay the combustion of the material.

Flash
Resin that is forced out of the mold cavity area and onto the parting line or into the vents of the mold. A very thin film of cured resin attached to the molded part.

Flash Pockets
Flash pockets provide relief areas outside the pinch-offs to limit the amount of compression for mold closing. The flash pockets are sometimes referred to as gutter or relief areas. Ideally, flash pockets will be deep enough to lessen the compression of the flash material, while providing enough surface contact to cool the flashed material.

Flashpoint
The temperature at which solvents volatilize sufficiently to produce a flammable mixture.

Flow
The ability of the molten resin to move or travel during injection. Flow can be influenced by temperature, part design, process conditions and tool design.

Flow Balancing
Modifying flow paths, particularly runner sections, so that all flow paths within a mold fill in equal time with equal pressure.

Flow Leader
A small area in the mold (usually no more than 0.200" to 0.300" wide) which locally thickens the wall to allow material to flow into outer areas more smoothly. A molders "trick" to get a few more inches of flow from the material. Usually not designed in the initial stage of tool construction. Use should be based on experience or qualified molder inputs. Also known as a flow rib.

Flow Pattern
The contour the melt takes sequentially as it fills the cavity. The mold should fill with a straight flow front with no changes in direction throughout filling. Mold-filling analysis software can be used to predict these flow patterns.

Flow Rate
The volume of material passing a fixed point per unit time.

Flow Restrictor
A small area in the mold which usually thins the wall to stall the flow of resin to select areas of the mold. Used to steer the material in another direction

Foaming
Foaming is the process of producing a cellular plastic by using foaming agents. A foaming agent is a material mixed with or dissolved in a plastic to make it foam. It includes expanding agents that produce gas on heating such as easily volatile solvents or chemical blowing agents that produce gas by thermal decomposition. Weight reduction is the percent volume of a foamed part which contains gas instead of resin. To get 10% weight reduction, the mold is filled 90%, then allowed to "foam" and fill that last 10%. Since only 90% of the volume is resin, the part weighs 10% less than a solid part of the same dimensions would. High weight reductions result in reduced material properties when compared to low weight reductions.

Foaming Agent
Any substance which alone or in combination with other substances is capable or producing a cellular structure in a plastic mass.

Forming
A general term encompassing processes in which the shape of plastic pieces such as sheets, rods or tubes is changed to a desired configuration.

Gate
In injection molding, the channel through which the molten resin flows from the runner into the cavity.

Gate Blush
A blemish or disturbance in the gate area of an injection molded article.

Hardness
The hardness of a material can be measured by its resistance to scratching or to indentation. Mostly used hardness tests involve the determination of the material resistance to indentation under standardized conditions. A hard indenter of standard shape is pressed into the surface of the material under a specified load. The resulting area of indentation or the depth of indentation is measured and assigned a numerical value. Various methods can be used. For plastics, the most widely used methods are Ball hardness, Rockwell and Shore methods.

Hold Pressure
The applied hydraulic injection pressure maintained after the completion of mold filling. Also referred to as secondary pressure.

Homopolymer
Homopolymers are polymers which are made up of one single repeated basic unit or (mono)mer.

Hopper
The device above the machine barrel used to store the resin pellets.

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